As a dietitian in the United States Army, many soldiers have sought nutritional advice from me with the goal of gaining muscle or bulking up before going to Ranger School. Many professional and recreational athletes likewise want to intentionally gain weight for reasons that include increased strength or power or being at a heavier body weight than the opponent to gain a competitive edge.
But current sports nutrition guidelines for intentional weight gain are based more on estimates and assumptions than evidence, as very little research has been conducted in this area. The commonly recommended starting point for an energy surplus is an additional 500 kcal per day, which may be incorporated by adding one or two additional energy-dense snacks or beverages. This additional energy may be from whole foods that have been minimally processed in consideration of both the health (short and long term) and performance of the athletic individual.
For our study, “A Randomized Trial of Healthy Weight Gain in Athletic Individuals,” recently published in Medicine & Science in Sport & Exercise®, we explored whether current performance nutrition guidelines of a ~500 kcal/day surplus along with rigorous resistance training promoted healthy weight gain, which we define as being mostly lean with minimal gains in adiposity and no ill health effects. We included 32 athletes (19 men, 13 women) from a variety of athletic backgrounds, as this accurately represents the reality of a sports dietitian’s work. Of note, we were able to recruit a number of female participants, an understudied population in this area of research.
Instead of providing participants with ultra-processed snacks, high-energy supplements or mass gainers, we prepared our 500 kcal snacks each week from minimally processed foods. To investigate a possible difference in healthy weight gain between the two commonly discussed macronutrients in sports nutrition, we randomized our participants to a protein-dominant or carbohydrate-dominant snack group. Two examples of our protein-dominant snacks include a smoothie (natural peanut butter, banana and whole milk) and a handful of peanuts, raisins and spicy cheese. Examples of our carbohydrate-dominant snacks include a smoothie (frozen blueberries, strawberries, fresh spinach, orange juice, avocado, extra-virgin olive oil and sugar) and a handful of dried mango, dried cranberries and butter crackers.
The key takeaway of our study is that current performance nutrition guidelines for healthy weight gain worked for about half of our participants by the end of our 10-week intervention, with no adverse health outcomes (fasting blood lipids, blood glucose and blood pressure). Furthermore, the total weight gain was about ~70% lean mass. A surprising result was that our carbohydrate-dominant snack group gained more weight than the protein-dominant snack group, though lean mass gain was not statistically different between groups.
We must continue to investigate what factors contributed to a more or less efficient weight gain among our participants, or in other words, what factors help explain why some athletes gain weight and others seem to be hard gainers. These factors likely include individual characteristics such as age, sex, resistance training history, hormonal profile and changes in metabolism or appetite that occur in response to energy surplus.
We hope nutrition and exercise professionals will use the results of our study to help their clients with healthy weight gain and may recommend the whole food approach. Because we found a wide range of weight gain among our participants (-0.9 to 4.4 kg), we also recommend frequently analyzing client progress to ensure the right energy surplus for optimal healthy weight gain.
This study was funded by a grant from the Peanut Institute Foundation.
The views and information presented are those of the author and do not represent the official position of the U.S. Army Medical Center of Excellence, the U.S. Army Training and Doctrine Command, or the Department of the Army, Department of Defense, or U.S. Government.
Allison Sanchez, Ph.D., recently earned her doctorate in clinical physiology and metabolism from Virginia Polytechnic Institute and State University. Her dissertation work focused on evaluating nutrition recommendations and identifying predictors to promote healthy weight gain through whole foods in athletic individuals. She has been a registered dietitian in the United States Army since 2011 and a board-certified specialist in sports dietetics since 2014. She is a member of the American College of Sports Medicine®.
